Semiconductor device and method for fabricating the same

ABSTRACT

A method for fabricating semiconductor device includes the steps of first providing a substrate having a fin-shaped structure thereon, forming a single diffusion break (SDB) structure in the substrate to divide the fin-shaped structure into a first portion and a second portion, and then forming more than one gate structures such as a first gate structure and a second gate structure on the SDB structure. Preferably, each of the first gate structure and the second gate structure overlaps the fin-shaped structure and the SDB structure.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a division of U.S. application Ser. No. 16/802,463filed on Feb. 26, 2020, which is a continuation-in-part application ofU.S. patent application Ser. No. 16/589,032, filed on Sep. 30, 2019,which is a division of U.S. application Ser. No. 16/030,871, filed onJul. 10, 2018, and the contents of which are included herein byreference.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The invention relates to a method for fabricating semiconductor device,and more particularly to a method for dividing fin-shaped structure toform single diffusion break (SDB) structure.

2. Description of the Prior Art

With the trend in the industry being towards scaling down the size ofthe metal oxide semiconductor transistors (MOS), three-dimensional ornon-planar transistor technology, such as fin field effect transistortechnology (FinFET) has been developed to replace planar MOStransistors. Since the three-dimensional structure of a FinFET increasesthe overlapping area between the gate and the fin-shaped structure ofthe silicon substrate, the channel region can therefore be moreeffectively controlled. This way, the drain-induced barrier lowering(DIBL) effect and the short channel effect are reduced. The channelregion is also longer for an equivalent gate length, thus the currentbetween the source and the drain is increased. In addition, thethreshold voltage of the fin FET can be controlled by adjusting the workfunction of the gate.

In current FinFET fabrication, after shallow trench isolation (STI) isformed around the fin-shaped structure part of the fin-shaped structureand part of the STI could be removed to form a trench, and insulatingmaterial is deposited into the trench to form single diffusion break(SDB) structure or isolation structure. However, the integration of theSDB structure and metal gate fabrication still remains numerousproblems. Hence how to improve the current FinFET fabrication andstructure has become an important task in this field.

SUMMARY OF THE INVENTION

According to an embodiment of the present invention, a method forfabricating semiconductor device includes the steps of: providing asubstrate having a first region and a second region; forming a firstfin-shaped structure on the first region; removing part of the firstfin-shaped structure to form a first trench; forming a dielectric layerin the first trench, wherein the dielectric layer comprises siliconoxycarbonitride (SiOCN); and planarizing the dielectric layer to form afirst single diffusion break (SDB) structure.

According to another aspect of the present invention, a semiconductordevice includes: a substrate having a first region and a second region;a first fin-shaped structure on the first region; and a first singlediffusion break (SDB) structure in the first fin-shaped structure todivide the first fin-shaped structure into a first portion and a secondportion. Preferably, the first SDB structure comprises siliconoxycarbonitride (SiOCN).

According to yet another aspect of the present invention, a method forfabricating semiconductor device includes the steps of first providing asubstrate having a fin-shaped structure thereon, forming a singlediffusion break (SDB) structure in the substrate to divide thefin-shaped structure into a first portion and a second portion, and thenforming more than one gate structures such as a first gate structure anda second gate structure on the SDB structure. Preferably, each of thefirst gate structure and the second gate structure overlaps thefin-shaped structure and the SDB structure.

According to yet another aspect of the present invention, asemiconductor device includes a fin-shaped structure on a substrate, asingle diffusion break (SDB) structure in the fin-shaped structure todivide the first fin-shaped structure into a first portion and a secondportion, and more than one gate structures such as a first gatestructure and a second gate structure disposed on the SDB structure.Preferably, each of the first gate structure and the second gatestructure overlaps the fin-shaped structure and the SDB structure.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top view illustrating a method for fabricating asemiconductor device according to an embodiment of the presentinvention.

FIGS. 2-7 illustrate a method for fabricating a semiconductor deviceaccording to an embodiment of the present invention.

FIG. 8 is a top view illustrating a method for fabricating asemiconductor device according to an embodiment of the presentinvention.

FIGS. 9-13 illustrate a method for fabricating a semiconductor deviceaccording to an embodiment of the present invention.

FIG. 14 illustrates a structural view of a semiconductor deviceaccording to an embodiment of the present invention.

FIG. 15 illustrates a structural view of a semiconductor deviceaccording to an embodiment of the present invention.

FIG. 16 illustrates a structural view of a semiconductor deviceaccording to an embodiment of the present invention.

FIG. 17 illustrates a structural view of a semiconductor deviceaccording to an embodiment of the present invention.

DETAILED DESCRIPTION

Referring to FIGS. 1-2 , in which FIG. 1 is a top view illustrating amethod for fabricating a semiconductor device according to an embodimentof the present invention, the left portion of FIG. 2 illustrates across-sectional view of FIG. 1 for fabricating the semiconductor devicealong the sectional line AA′, and the right portion of FIG. 2illustrates a cross-sectional view of FIG. 1 for fabricating thesemiconductor device along the sectional line BB′. As shown in FIGS. 1-2, a substrate 12, such as a silicon substrate or silicon-on-insulator(SOI) substrate is first provided, a first region such as a NMOS region14 and a second region such as a PMOS region 16 are defined on thesubstrate 12, and at least a fin-shaped structure 18 is formed on eachof the NMOS region 14 and PMOS region 16. It should be noted that eventhough four fin-shaped structures 18 are disposed on each of thetransistor regions in this embodiment, it would also be desirable toadjust the number of fin-shaped structures 18 depending on the demand ofthe product, which is also within the scope of the present invention.

Preferably, the fin-shaped structures 18 of this embodiment could beobtained by a sidewall image transfer (SIT) process. For instance, alayout pattern is first input into a computer system and is modifiedthrough suitable calculation. The modified layout is then defined in amask and further transferred to a layer of sacrificial layer on asubstrate through a photolithographic and an etching process. In thisway, several sacrificial layers distributed with a same spacing and of asame width are formed on a substrate. Each of the sacrificial layers maybe stripe-shaped. Subsequently, a deposition process and an etchingprocess are carried out such that spacers are formed on the sidewalls ofthe patterned sacrificial layers. In a next step, sacrificial layers canbe removed completely by performing an etching process. Through theetching process, the pattern defined by the spacers can be transferredinto the substrate underneath, and through additional fin cut processes,desirable pattern structures, such as stripe patterned fin-shapedstructures could be obtained.

Alternatively, the fin-shaped structures 18 could also be obtained byfirst forming a patterned mask (not shown) on the substrate, 12, andthrough an etching process, the pattern of the patterned mask istransferred to the substrate 12 to form the fin-shaped structures 18.Moreover, the formation of the fin-shaped structures 18 could also beaccomplished by first forming a patterned hard mask (not shown) on thesubstrate 12, and a semiconductor layer composed of silicon germanium isgrown from the substrate 12 through exposed patterned hard mask viaselective epitaxial growth process to form the corresponding fin-shapedstructures 18. These approaches for forming fin-shaped structure are allwithin the scope of the present invention. It should be noted that afterthe fin-shaped structures 18 are formed, a liner 22 made of siliconoxide could be formed on the surface of the fin-shaped structures 18 onthe NMOS region 14 and PMOS region 16.

Next, a shallow trench isolation (STI) 20 is formed around thefin-shaped structures 18. In this embodiment, the formation of the STI20 could be accomplished by conducting a flowable chemical vapordeposition (FCVD) process to form a silicon oxide layer on the substrate12 and covering the fin-shaped structures 18 entirely. Next, a chemicalmechanical polishing (CMP) process along with an etching process areconducted to remove part of the silicon oxide layer so that the topsurface of the remaining silicon oxide is slightly lower than the topsurface of the fin-shaped structures 18 for forming the STI 20.

Next, as shown in FIG. 2 , an etching process is conducted by using apatterned mask (not shown) as mask to remove part of the liner 22 andpart of the fin-shaped structures 18 to form trenches 24, in which eachof the trenches 24 preferably divides each of the fin-shaped structures18 disposed on the NMOS region 14 and PMOS region 16 into two portions,including a portion 26 on the left side of the trench 24 and a portion28 on the right side of the trench 24.

Next, as shown in FIG. 3 , an oxidation process is conducted to formanother liner 30 made of silicon oxide in the trenches 24 on the NMOSregion 14 and PMOS region 16, in which the liner 30 is disposed on thebottom surface and two sidewalls of the trenches 24 and contacting theliner 22 directly. Next, a dielectric layer 32 is formed in the trenches24 and filling the trenches 24 completely, and a planarizing processsuch as chemical mechanical polishing (CMP) process and/or etchingprocess is conducted to remove part of the dielectric layer 32 so thatthe top surface of the remaining dielectric layer 32 is even with orslightly higher than the top surface of the fin-shaped structures 18.This forms SDB structures 34, 36 on the NMOS region 14 and PMOS region16 respectively.

As shown in FIG. 1 , each of the fin-shaped structures 18 on the NMOSregion 14 and PMOS region 16 are disposed extending along a firstdirection (such as X-direction) while the SDB structures 34, 36 aredisposed extending along a second direction (such as Y-direction), inwhich the first direction is orthogonal to the second direction.

It should be noted that the dielectric layer 32 and the liner 30 in thisembodiment are preferably made of different materials, in which theliner 30 is preferably made of silicon oxide and the dielectric layer 32is made of silicon oxycarbonitride (SiOCN). Specifically, the SDBstructures 34, 36 made of SiOCN in this embodiment are preferablystructures having low stress, in which the concentration proportion ofoxygen within SiOCN is preferably between 30% to 60% and the stress ofeach of the SDB structures 34, 36 is between 100 MPa to −500 MPa or mostpreferably at around 0 MPa. In contrast to the conventional SDBstructures made of dielectric material such as silicon oxide or siliconnitride, the SDB structures of this embodiment made of low stressmaterial such as SiOCN could increase the performance of on/off currentin each of the transistors thereby boost the performance of the device.

Next, as shown in FIG. 4 , an ion implantation process could beconducted to form deep wells or well regions in the fin-shapedstructures 18 on the NMOS region 14 and PMOS region 16, and a cleanprocess could be conducted by using diluted hydrofluoric acid (dHF) toremove the liner 22 on the surface of the fin-shaped structures 18completely, part of the liner 30 on sidewalls of the trenches 24, andeven part of the SDB structures 34, 36. This exposes the surface of thefin-shaped structures 18 and the top surfaces of the remaining liner 30and the SDB structures 34, 36 are slightly lower than the top surface ofthe fin-shaped structures 18 while the top surface of the SDB structures34 36 is also slightly higher than the top surface of the remainingliner 30.

Next, as shown in FIG. 5 , at least a gate structure such as gatestructures 38, 40 or dummy gates are formed on the fin-shaped structures18 on the NMOS region 14 and PMOS region 16. In this embodiment, theformation of the first gate structure 38, 40 could be accomplished by agate first process, a high-k first approach from gate last process, or ahigh-k last approach from gate last process. Since this embodimentpertains to a high-k last approach, a gate dielectric layer 42 orinterfacial layer, a gate material layer 44 made of polysilicon, and aselective hard mask could be formed sequentially on the substrate 12 orfin-shaped structures 18, and a photo-etching process is then conductedby using a patterned resist (not shown) as mask to remove part of thegate material layer 44 and part of the gate dielectric layer 42 throughsingle or multiple etching processes. After stripping the patternedresist, gate structures 38, 40 each composed of a patterned gatedielectric layer 42 and a patterned material layer 44 are formed on thefin-shaped structures 18.

Next, at least a spacer 46 is formed on sidewalls of the each of thegate structures 38, 40, a source/drain region 48 and/or epitaxial layer50 is formed in the fin-shaped structure 18 adjacent to two sides of thespacer 46, and selective silicide layers (not shown) could be formed onthe surface of the source/drain regions 48. In this embodiment, each ofthe spacers 46 could be a single spacer or a composite spacer, such as aspacer including but not limited to for example an offset spacer and amain spacer. Preferably, the offset spacer and the main spacer couldinclude same material or different material while both the offset spacerand the main spacer could be made of material including but not limitedto for example SiO₂, SiN, SiON, SiCN, or combination thereof. Thesource/drain regions 48 and epitaxial layers 50 could include differentdopants and/or different materials depending on the conductive type ofthe device being fabricated. For instance, the source/drain region 48 onthe NMOS region 14 could include n-type dopants and the epitaxial layer50 on the same region could include silicon phosphide (SiP) while thesource/drain region 48 on the PMOS region 16 could include p-typedopants and the epitaxial layer 50 on the same region could includesilicon germanium (SiGe).

Next, as shown in FIG. 6 , a contact etch stop layer (CESL) 52 is formedon the surface of the fin-shaped structures 18 and covering the gatestructures 38, 40, and an interlayer dielectric (ILD) layer 54 is formedon the CESL 52. Next, a planarizing process such as CMP is conducted toremove part of the ILD layer 54 and part of the CESL 52 for exposing thegate material layer 44 made of polysilicon, in which the top surface ofthe gate material layer 44 is even with the top surface of the ILD layer54.

Next, a replacement metal gate (RMG) process is conducted to transformthe gate structures 38, 40 into metal gates 58, 60. For instance, theRMG process could be accomplished by first performing a selective dryetching or wet etching process using etchants including but not limitedto for example ammonium hydroxide (NH₄OH) or tetramethylammoniumhydroxide (TMAH) to remove the gate material layer 44 and even gatedielectric layer 42 from the gate structures 38, 40 for forming recesses56 in the ILD layer 54.

Next, as shown in FIG. 7 , a selective interfacial layer or gatedielectric layer 62, a high-k dielectric layer 64, a work function metallayer 66, and a low resistance metal layer 68 are formed in the recesses56, and a planarizing process such as CMP is conducted to remove part oflow resistance metal layer 68, part of work function metal layer 66, andpart of high-k dielectric layer 64 to form metal gates 58, 60. Next,part of the low resistance metal layer 68, part of the work functionmetal layer 66, and part of the high-k dielectric layer 64 are removedto form a recess (not shown) on each of the transistor region, and ahard mask 70 made of dielectric material including but not limited tofor example silicon nitride is deposited into the recesses so that thetop surfaces of the hard mask 70 and ILD layer 54 are coplanar. In thisembodiment, each of the gate structures or metal gates 58, 60 fabricatedthrough high-k last process of a gate last process preferably includesan interfacial layer or gate dielectric layer 62, a U-shaped high-kdielectric layer 64, a U-shaped work function metal layer 66, and a lowresistance metal layer 68.

In this embodiment, the high-k dielectric layer 64 is preferablyselected from dielectric materials having dielectric constant (k value)larger than 4. For instance, the high-k dielectric layer 64 may beselected from hafnium oxide (HfO₂), hafnium silicon oxide (HfSiO₄),hafnium silicon oxynitride (HfSiON), aluminum oxide (Al₂O₃), lanthanumoxide (La₂O₃), tantalum oxide (Ta₂O₅), yttrium oxide (Y₂O₃), zirconiumoxide (ZrO₂), strontium titanate oxide (SrTiO₃), zirconium silicon oxide(ZrSiO₄), hafnium zirconium oxide (HfZrO₄), strontium bismuth tantalate(SrBi₂Ta₂O₉, SBT), lead zirconate titanate (PbZr_(x)Ti_(1-x)O₃, PZT),barium strontium titanate (Ba_(x)Sr_(1-x)TiO₃, BST) or a combinationthereof.

In this embodiment, the work function metal layer 66 is formed fortuning the work function of the metal gate in accordance with theconductivity of the device. For an NMOS transistor, the work functionmetal layer 66 having a work function ranging between 3.9 eV and 4.3 eVmay include titanium aluminide (TiAl), zirconium aluminide (ZrAl),tungsten aluminide (WAl), tantalum aluminide (TaAl), hafnium aluminide(HfAl), or titanium aluminum carbide (TiAlC), but it is not limitedthereto. For a PMOS transistor, the work function metal layer 66 havinga work function ranging between 4.8 eV and 5.2 eV may include titaniumnitride (TiN), tantalum nitride (TaN), tantalum carbide (TaC), but it isnot limited thereto. An optional barrier layer (not shown) could beformed between the work function metal layer 66 and the low resistancemetal layer 68, in which the material of the barrier layer may includetitanium (Ti), titanium nitride (TiN), tantalum (Ta) or tantalum nitride(TaN). Furthermore, the material of the low-resistance metal layer 68may include copper (Cu), aluminum (Al), titanium aluminum (TiAl), cobalttungsten phosphide (CoWP) or any combination thereof.

Next, a pattern transfer process is conducted by using a patterned mask(not shown) as mask to remove part of the ILD layer 54 and part of theCESL 52 for forming contact holes (not shown) exposing the source/drainregions 48 underneath. Next, metals including a barrier layer selectedfrom the group consisting of Ti, TiN, Ta, and TaN and a low resistancemetal layer selected from the group consisting of W, Cu, Al, TiAl, andCoWP are deposited into the contact holes, and a planarizing processsuch as CMP is conducted to remove part of aforementioned barrier layerand low resistance metal layer for forming contact plugs 72 electricallyconnecting the source/drain regions 48. This completes the fabricationof a semiconductor device according to a preferred embodiment of thepresent invention.

It should be noted that even though SDB structures 34, 36 are formed onthe NMOS region 14 and PMOS region 16 at the same time in theaforementioned embodiment, it would also be desirable to follow theaforementioned process to form SDB structure only on the NMOS region 14or the PMOS region 16 and then conduct gate structure formation and RMGprocess afterwards, which is also within the scope of the presentinvention.

Preferably, the present invention first forms fin-shaped structures onthe NMOS region and/or PMOS region, divides each of the fin-shapedstructures into two portions by forming at least a trench in thefin-shaped structures, and then deposits a dielectric material into thetrenches on both transistors at the same time to form SDB structures.According to a preferred embodiment of the present invention, the SDBstructures formed on the NMOS region and PMOS region are preferably madeof SiOCN, in which the proportion of oxygen concentration in SiOCN ispreferably between 30% to 60% and the stress of each of the SDBstructures 34, 36 is preferably between 100 MPa to −500 MPa. In contrastto the conventional SDB structures made of dielectric material such assilicon oxide or silicon nitride, the SDB structures of the presentinvention made of low stress material such as SiOCN could increase theperformance of on/off current in each of the transistors and boost theperformance of the device substantially.

Referring to FIGS. 8-9 , FIG. 8 is a top view illustrating a method forfabricating a semiconductor device according to an embodiment of thepresent invention and FIG. 9 illustrates a cross-sectional view of FIG.8 for fabricating the semiconductor device along the sectional line CC′.As shown in FIGS. 8-9 , a substrate 12, such as a silicon substrate orsilicon-on-insulator (SOI) substrate is first provided, a transistorregion such as a NMOS region or a PMOS region is defined on thesubstrate 12, and at least a fin-shaped structure 18 is formed on thesubstrate. It should be noted that even though four fin-shapedstructures 18 are disposed on each of the transistor regions in thisembodiment, it would also be desirable to adjust the number offin-shaped structures 18 depending on the demand of the product, whichis also within the scope of the present invention. Moreover, elementssuch as fin-shaped structures, gate structures, CESL, ILD layer, andmetal gate elements disclosed in the aforementioned embodiment arelabeled with same numberings for simplicity purpose.

Similar to the aforementioned embodiment, the fin-shaped structures 18of this embodiment could be obtained by a sidewall image transfer (SIT)process. For instance, a layout pattern is first input into a computersystem and is modified through suitable calculation. The modified layoutis then defined in a mask and further transferred to a layer ofsacrificial layer on a substrate through a photolithographic and anetching process. In this way, several sacrificial layers distributedwith a same spacing and of a same width are formed on a substrate. Eachof the sacrificial layers may be stripe-shaped. Subsequently, adeposition process and an etching process are carried out such thatspacers are formed on the sidewalls of the patterned sacrificial layers.In a next step, sacrificial layers can be removed completely byperforming an etching process. Through the etching process, the patterndefined by the spacers can be transferred into the substrate underneath,and through additional fin cut processes, desirable pattern structures,such as stripe patterned fin-shaped structures could be obtained.

Alternatively, the fin-shaped structures 18 could also be obtained byfirst forming a patterned mask (not shown) on the substrate, 12, andthrough an etching process, the pattern of the patterned mask istransferred to the substrate 12 to form the fin-shaped structures 18.Moreover, the formation of the fin-shaped structures 18 could also beaccomplished by first forming a patterned hard mask (not shown) on thesubstrate 12, and a semiconductor layer composed of silicon germanium isgrown from the substrate 12 through exposed patterned hard mask viaselective epitaxial growth process to form the corresponding fin-shapedstructures 18. These approaches for forming fin-shaped structure are allwithin the scope of the present invention. After the fin-shapedstructures 18 are formed, a liner 22 made of silicon oxide could beformed on the surface of the fin-shaped structures 18.

Next, a shallow trench isolation (STI) 20 is formed around thefin-shaped structures 18. In this embodiment, the formation of the STI20 could be accomplished by conducting a flowable chemical vapordeposition (FCVD) process to form a silicon oxide layer on the substrate12 and covering the fin-shaped structures 18 entirely. Next, a chemicalmechanical polishing (CMP) process along with an etching process areconducted to remove part of the silicon oxide layer so that the topsurface of the remaining silicon oxide is slightly lower than the topsurface of the fin-shaped structures 18 for forming the STI 20.

Next, as shown in FIG. 9 , an etching process is conducted by using apatterned mask (not shown) as mask to remove part of the liner 22 andpart of the fin-shaped structures 18 to form a trench 24, in which thetrench 24 preferably divides the fin-shaped structure 18 into twoportions, including a portion 26 on the left side of the trench 24 and aportion 28 on the right side of the trench 24.

Next, as shown in FIG. 10 , an oxidation process is conducted to formanother liner 30 made of silicon oxide in the trench 24, in which theliner 30 is disposed on the bottom surface and two sidewalls of thetrench 24 and contacting the liner 22 directly. Next, a dielectric layer32 is formed in the trench 24 to fill the trench 24 completely, and aplanarizing process such as chemical mechanical polishing (CMP) processand/or etching process is conducted to remove all of the liner 22 andpart of the dielectric layer 32 so that the top surface of the remainingdielectric layer 32 is even with or slightly higher than the top surfaceof the fin-shaped structure 18. This forms a SDB structure 34 in thefin-shaped structure.

As shown in FIG. 8 , each of the fin-shaped structures 18 are disposedextending along a first direction (such as X-direction) while the SDBstructure 34 is disposed extending along a second direction (such asY-direction), in which the first direction is orthogonal to the seconddirection.

It should be noted that the dielectric layer 32 and the liner 30 in thisembodiment are preferably made of different materials, in which theliner 30 is preferably made of silicon oxide and the dielectric layer 32is made of silicon oxycarbonitride (SiOCN). Specifically, the SDBstructure 34 made of SiOCN in this embodiment preferably has low stress,in which the concentration proportion of oxygen within SiOCN ispreferably between 30% to 60% and the stress of the SDB structure 34 isbetween 100 MPa to −500 MPa or most preferably at around 0 MPa. Incontrast to the conventional SDB structures made of dielectric materialsuch as silicon oxide or silicon nitride, the SDB structures of thisembodiment made of low stress material such as SiOCN could increase theperformance of on/off current in each of the transistors thereby boostthe performance of the device.

Next, as shown in FIG. 11 , more than one gate structures such as gatestructures 38, 40 or dummy gates are formed on the fin-shaped structure18 and the SDB structure 34 as each of the gate structures 38, 40overlaps the fin-shaped structure 18 and the SDB structure 34 at thesame time. In contrast to the gate structures 38, 40 of theaforementioned embodiment are disposed on the NMOS region 14 and PMOSregion 16 respectively, both the gate structures 38, 40 in thisembodiment are disposed on the same transistor region such as a NMOSregion or PMOS region. In this embodiment, the formation of the gatestructure 38, 40 could be accomplished by a gate first process, a high-kfirst approach from gate last process, or a high-k last approach fromgate last process. Since this embodiment pertains to a high-k lastapproach, a gate dielectric layer 42 or interfacial layer, a gatematerial layer 44 made of polysilicon, and a selective hard mask couldbe formed sequentially on the substrate 12 or fin-shaped structures 18,and then a sidewall image transfer (SIT) process is conducted to patternthe gate material layer into more than one gate structures.

Preferably, the SIT process could be accomplished by first forming aplurality of mandrels (not shown) on the gate material layer 44. In thisembodiment, the fabrication of the mandrels (not shown) could beaccomplished by first forming a material layer (not shown) on the gatematerial layer 44, and a pattern transfer process is conducted by usingetching to remove part of the material layer for forming a plurality ofpatterned material layers serving as mandrels on the gate material layer44. Preferably, the mandrels could be selected from the group consistingof amorphous silicon, polysilicon, silicon oxide, and silicon nitride,but not limited thereto.

Next, a spacer (not shown) is formed adjacent to each of the mandrels,in which the spacers could be selected from the group consisting ofsilicon oxide, silicon nitride, silicon oxynitride (SiON), and siliconcarbon nitride (SiCN), but not limited thereto. Next, the mandrels areremoved completely, and the remaining spacers are used as mask toperform another etching process to pattern or remove part of the gatematerial layer 44 and gate dielectric layer 42 for forming more than onegate structures such as the gate structures 38, 40 standing on thefin-shaped structure 18 and the SDB structure 34.

Next, at least a spacer 46 is formed on sidewalls of the each of thegate structures 38, 40, a source/drain region 48 and/or epitaxial layer50 is formed in the fin-shaped structure 18 adjacent to the spacer 46,and selective silicide layers (not shown) could be formed on the surfaceof the source/drain regions 48. In this embodiment, each of the spacers46 could be a single spacer or a composite spacer, such as a spacerincluding but not limited to for example an offset spacer and a mainspacer. Preferably, the offset spacer and the main spacer could includesame material or different material while both the offset spacer and themain spacer could be made of material including but not limited to forexample SiO₂, SiN, SiON, SiCN, or combination thereof.

The source/drain regions 48 and epitaxial layers 50 could includedifferent dopants and/or different materials depending on the conductivetype of the device being fabricated. For instance, the source/drainregion 48 on the NMOS region could include n-type dopants and theepitaxial layer 50 on the same region could include silicon phosphide(SiP) while the source/drain region 48 on the PMOS region could includep-type dopants and the epitaxial layer 50 on the same region couldinclude silicon germanium (SiGe). It should be noted that thesource/drain regions 48 adjacent to the gate structures 38, 40 arepreferably made of same material having same conductive type and thesource/drain regions 48 are only formed in the fin-shaped structure 18adjacent to the gate structures 38, 40 but not within the SDB structure34 between the gate structures 38, 40.

Next, as shown in FIG. 12 , a contact etch stop layer (CESL) 52 isformed on the surface of the fin-shaped structures 18 and covering thegate structures 38, 40, and an interlayer dielectric (ILD) layer 54 isformed on the CESL 52. Next, a planarizing process such as CMP isconducted to remove part of the ILD layer 54 and part of the CESL 52 forexposing the gate material layer 44 made of polysilicon, in which thetop surface of the gate material layer 44 is even with the top surfaceof the ILD layer 54.

Next, a replacement metal gate (RMG) process is conducted to transformthe gate structures 38, 40 into metal gates 58, 60. For instance, theRMG process could be accomplished by first performing a selective dryetching or wet etching process using etchants including but not limitedto for example ammonium hydroxide (NH₄OH) or tetramethylammoniumhydroxide (TMAH) to remove the gate material layer 44 and even gatedielectric layer 42 from the gate structures 38, 40 for forming recesses56 in the ILD layer 54.

Next, as shown in FIG. 13 , a selective interfacial layer or gatedielectric layer 62, a high-k dielectric layer 64, a work function metallayer 66, and a low resistance metal layer 68 are formed in the recesses56, and a planarizing process such as CMP is conducted to remove part oflow resistance metal layer 68, part of work function metal layer 66, andpart of high-k dielectric layer 64 to form metal gates 58, 60. Next,part of the low resistance metal layer 68, part of the work functionmetal layer 66, and part of the high-k dielectric layer 64 are removedto form a recess (not shown) on each of the transistor region, and ahard mask 70 made of dielectric material including but not limited tofor example silicon nitride is deposited into the recesses so that thetop surfaces of the hard mask 70 and ILD layer 54 are coplanar. In thisembodiment, each of the gate structures or metal gates 58, 60 fabricatedthrough high-k last process of a gate last process preferably includesan interfacial layer or gate dielectric layer 62, a U-shaped high-kdielectric layer 64, a U-shaped work function metal layer 66, and a lowresistance metal layer 68.

In this embodiment, the high-k dielectric layer 64 is preferablyselected from dielectric materials having dielectric constant (k value)larger than 4. For instance, the high-k dielectric layer 64 may beselected from hafnium oxide (HfO₂), hafnium silicon oxide (HfSiO₄),hafnium silicon oxynitride (HfSiON), aluminum oxide (Al₂O₃), lanthanumoxide (La₂O₃), tantalum oxide (Ta₂O₅), yttrium oxide (Y₂O₃), zirconiumoxide (ZrO₂), strontium titanate oxide (SrTiO₃), zirconium silicon oxide(ZrSiO₄), hafnium zirconium oxide (HfZrO₄), strontium bismuth tantalate(SrBi₂Ta₂O₉, SBT), lead zirconate titanate (PbZr_(x)Ti_(1-x)O₃, PZT),barium strontium titanate (Ba_(x)Sr_(1-x)TiO₃, BST) or a combinationthereof.

In this embodiment, the work function metal layer 66 is formed fortuning the work function of the metal gate in accordance with theconductivity of the device. For an NMOS transistor, the work functionmetal layer 66 having a work function ranging between 3.9 eV and 4.3 eVmay include titanium aluminide (TiAl), zirconium aluminide (ZrAl),tungsten aluminide (WAl), tantalum aluminide (TaAl), hafnium aluminide(HfAl), or titanium aluminum carbide (TiAlC), but it is not limitedthereto. For a PMOS transistor, the work function metal layer 66 havinga work function ranging between 4.8 eV and 5.2 eV may include titaniumnitride (TiN), tantalum nitride (TaN), tantalum carbide (TaC), but it isnot limited thereto. An optional barrier layer (not shown) could beformed between the work function metal layer 66 and the low resistancemetal layer 68, in which the material of the barrier layer may includetitanium (Ti), titanium nitride (TiN), tantalum (Ta) or tantalum nitride(TaN). Furthermore, the material of the low-resistance metal layer 68may include copper (Cu), aluminum (Al), titanium aluminum (TiAl), cobalttungsten phosphide (CoWP) or any combination thereof.

Next, a pattern transfer process is conducted by using a patterned mask(not shown) as mask to remove part of the ILD layer 54 and part of theCESL 52 for forming contact holes (not shown) exposing the source/drainregions 48 underneath. Next, metals including a barrier layer selectedfrom the group consisting of Ti, TiN, Ta, and TaN and a low resistancemetal layer selected from the group consisting of W, Cu, Al, TiAl, andCoWP are deposited into the contact holes, and a planarizing processsuch as CMP is conducted to remove part of aforementioned barrier layerand low resistance metal layer for forming contact plugs 72 electricallyconnecting the source/drain regions 48. This completes the fabricationof a semiconductor device according to a preferred embodiment of thepresent invention.

Referring to FIG. 14 , FIG. 14 illustrates a structural view of asemiconductor device according to an embodiment of the presentinvention. As shown in FIG. 14 , in contrast to the aforementionedembodiment of disposing two gate structures 38, 40 on the SDB structure34 while the gate structures 38, 40 overlapping both the fin-shapedstructure 18 and the SDB structure 34 at the same time, it would also bedesirable to adjust the position of the gate structures 38, 40 so thatthe sidewalls of the gate structures 38, 40 are aligned with thesidewalls of the SDB structure 34 as the gate structures 38, 40 are onlydisposed on top of the SDB structure 34 without overlapping thefin-shaped structure 18, which is also within the scope of the presentinvention.

Referring to FIG. 15 , FIG. 15 illustrates a structural view of asemiconductor device according to an embodiment of the presentinvention. As shown in FIG. 15 , in contrast to the embodiment from FIG.14 of aligning sidewalls of the gate structures 38, 40 to the sidewallsof the SDB structure 34, it would also be desirable to move the gatestructures 38, 40 further inward so that the gate structures 38, 40 aredisposed on top of the SDB structure 34 and not overlapping thefin-shaped structure 18 while sidewalls of the gate structures 38, 40are not aligned with edges of the SDB structure 34. Specifically, thesidewalls of the spacers 46 adjacent to the gate structure 38, 40 couldbe aligned with the sidewalls of the SDB structure 34 in this instance.

Referring to FIG. 16 , FIG. 16 illustrates a structural view of asemiconductor device according to an embodiment of the presentinvention. As shown in FIG. 16 , in contrast to only disposing two gatestructures 38, 40 or metal gates 58, 60 on the SDB structure 34 and thefin-shaped structure 18 in the aforementioned embodiments, it would alsobe desirable to adjust the pattern of mandrels and spacers used duringthe SIT process for producing more than two gate structures such as fourgate structures on the SDB structure 34 and the fin-shaped structure 18.Preferably, two gate structures 38, 40 or metal gates 58, 60 aredisposed on the two sides while two additional gate structures or metalgates 78, 80 are disposed directly on top of the SDB structure 34 andbetween the metal gates 58, 60 without overlapping the fin-shapedstructure 18.

Preferably, the two gate structures 38, 40 or metal gates 58, 60 couldbe disposed according to the manner suggested in the aforementionedembodiments. For instance, the metal gates 58, 60 could be disposed withsidewalls of spacers 46 aligned to the sidewalls of the SDB structure 34as shown in FIG. 16 , the metal gates 58, 60 could be disposed withsidewalls of the metal gates 58, 60 aligned to the sidewalls of the SDBstructure 34 as shown in FIG. 14 , or the metal gates 58, 60 could bedisposed while overlapping the SDB structure 34 fin-shaped structure 18at the same time as shown in FIG. 13 , which are all within the scope ofthe present invention. It should be noted that through SIT process, itwould be desirable to reduce the size of the gate structures beingformed so that more than one gate structures or metal gates could beformed on the SDB structure 34 and/or fin-shaped structure 18 at thesame time while maintaining the size of the SDB structure 34.

Referring to FIG. 17 , FIG. 17 illustrates a structural overview of asemiconductor device taken along the sectional line DD′ of FIG. 8according to an embodiment of the present invention. As shown in FIG. 17, the aforementioned gate structures 38, 40 or metal gates 58, 60 aredisposed on the SDB structure 34 and/or fin-shaped structures 18, twogate structures or metal gates 82, 88 are disposed on edges of thefin-shaped structures 18 and the STI 20 at the same time, a gatestructure or metal gate 84 is disposed on the fin-shaped structure 18between metal gates 58, 80, and another gate structure or metal gate 86is disposed on the fin-shaped structure 18 between metal gates 60, 88.Preferably, the top surface of the SDB structure 34 is even with the topsurface of the fin-shaped structure 18 while the top surface of the STI20 is lower than the top surfaces of the fin-shaped structure 18 and theSDB structure 34. The bottom surface of the SDB structure 34 could beeven with the bottom surface of the STI 20 in this instance or could belower than or higher than the bottom surface of the STI 20 according toother embodiments of the present invention, which are all within thescope of the present invention.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the invention. Accordingly, the abovedisclosure should be construed as limited only by the metes and boundsof the appended claims.

What is claimed is:
 1. A method for fabricating semiconductor device,comprising: providing a substrate having a fin-shaped structure thereon;forming a single diffusion break (SDB) structure in the substrate todivide the fin-shaped structure into a first portion and a secondportion, wherein the SDB structure comprises silicon oxycarbonitride(SiOCN); and forming more than one gate structures on the SDB structure.